Sulfur removal system

ABSTRACT

A sulfur removal system including a first reactor and a second reactor that are located in series to one another each having an adsorbent that includes cobalt and copper on an activated carbon support, a method of desulfurizing a sulfur-containing hydrocarbon stream via the sulfur removal system, and a method of making the adsorbent. Various embodiments of the sulfur removal system, the desulfurizing method, and the method of making the adsorbent is also provided.

STATEMENT OF FUNDING ACKNOWLEDGEMENT

The support provided by King Abdulaziz City for Science and Technology(KACST) through the Science & Technology Unit at King Fahd University ofPetroleum & Minerals (KFUPM) for funding through a project no.13-PET393-04 as part of the National Science, Technology and InnovationPlan is acknowledged.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to a sulfur removal system with a firstand a second reactor and an adsorbent that includes cobalt and copper onan activated carbon support.

DESCRIPTION OF THE RELATED ART

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Hydro-desulfurization is a common method of desulfurization that iswidely used in refineries. This method, however, requires a hightemperature, a high pressure, and a large catalyst volume [C. Song, Fuelprocessing for low-temperature and high-temperature fuel cells:challenges, and opportunities for sustainable development in the 21stcentury, Catal. Today 77 (2002) 17-49; D. D. Whitehurst, T. Isoda, andI. Mochida, Present State of the Art and Future Challenges in theHydrodesulfurization of Polyaromatic Sulfur Compounds, Elsevier MassonSAS 42 (1998) 345-471; R. Shafi and G. J. Hutchings,Hydrodesulfurization of hindered dibenzothiophenes: an overview, Catal.,Today 59 (2000), 423-422]. Therefore, adsorptive desulfurization hasbeen considered as an alternative desulfurization technique thatprovides relatively mild operating conditions and higher selectivity forthiophenic compounds compared to hydro-desulfurization techniques. Inaddition, adsorptive desulfurization can provide nearly 100% sulfurremoval when a suitable adsorbent is used [I. Ahmed, S. H. Jhung,Composites of metal-organic frameworks: Preparation and application inadsorption, Mater. Today 17 (2014) 136-146; J. M. Palomino, D. T. Tran,A. R. Kareh, C. A. Miller, J. M. V Gardner, H. Dong, S. J. Oliver,Zirconia-silica based mesoporous desulfurization adsorbents, J. PowerSources. 278 (2015) 141-148].

Selecting a suitable adsorbent is important for an efficient adsorptivedesulfurization process. It has been shown that metal oxides are amonggood sulfur adsorbents that are functional at high temperatures. Variousmetal oxides have been reported as efficient sulfur adsorbents due totheir high affinity to sulfur. Exemplary metal oxides include Zn, Mn,Cu, Co, Ni, Cr, Ca, and Fe [H. F. Garces, H. M. Galindo, L. J. Garces,J. Hunt, A. Morey, S. L. Suib, Low temperature H₂S dry-desulfurizationwith zinc oxide, Microporous Mesoporous Mater. 127 (2010) 190-197; J.Bin Chung, J. S. Chung, Desulfurization of H₂S using cobalt-containingsorbents at low temperatures, Chem. Eng. Sci. 60 (2005) 1515-1523; H. F.Garces, A. E. Espinal, S. L. Suib, Tunable shape microwave synthesis ofzinc oxide nanospheres and their desulfurization performance comparedwith nanorods and platelet-like morphologies for the removal of hydrogensulfide, J. Phys. Chem. C. 116 (2012) 8465-8474; M.Flytzani-Stephanopoulos, M. Sakbodin, Z. Wang, Regenerative Adsorptionand Removal of H₂S from Hot Fuel Gas Streams by Rare Earth Oxides,Science, 312 (2006) 1508-1510; E. Richter, Chemical Reactions as a Meansof Separation: Sulfur Removal, Chemie Ing. Tech. 50 (1978) 698-698; T.A. Saleh, G. I. Danmaliki, Adsorptive desulfurization ofdibenzothiophene from fuels by rubber tires-derived carbons: Kineticsand isotherms evaluation, Process Safety and Environmental Protection102 (2016) 9-19; G. I. Danmaliki, T. A. Saleh, Influence of conversionparameters of waste tires to activated carbon on adsorption ofdibenzothiophene from model fuels, Journal of Cleaner Production, 117(2016) 50-55; T. A. Saleh, G. I. Danmaliki, Influence of acidic andbasic treatments of activated carbon derived from waste rubber tires onadsorptive desulfurization of thiophenes, Journal of the TaiwanInstitute of Chemical Engineers, 60 (2016) 460-468; T. A. Saleh, Theinfluence of treatment temperature on the acidity of MWCNT oxidized byHNO₃ or a mixture of HNO₃/H₂SO₄, Applied Surface Science, 257 (2011)7746-7751]. On the other hand, various methods have been developed toenhance the performance of an adsorptive desulfurization process.Accordingly, researchers have investigated the performance of anadsorptive desulfurization process by doping metals or metal oxides ontosulfur adsorbents. For example, Ca—Ba, Zinc ferrite (ZnxFe₃-xO₄),Cu—Cr—O and Cu—Ce—O adsorbents have been successfully utilized in anadsorptive desulfurization process at high temperature [M. Stemmler, A.Tamburro, M. Muller, Laboratory investigations on chemical hot gascleaning of inorganic trace elements for the ‘UNIQUE’ process, Fuel, 108(2013) 31-36; R. E. Anala, D. W. Marsh, Characterization and Long-RangeReactivity of Zinc Ferrite in High-Temperature DesulfurizationProcessed, Ind. Eng. Chem. Res. 30, (1991) 55-60; Z. Li, M.Flytzani-stephanopoulos, Cu—Cr—O and Cu—Ce—O Regenerable Oxide Sorbentsfor Hot Gas Desulfurization, 36 (1997) 187-196]. In a separate study,these metals or metal oxides have been placed on a surface of one ormore adsorptive supports e.g. silica, alumina, zeolite, or activatedcarbon in order to boost the number of active adsorptive sites of theadsorbents. Among these adsorptive supports, activated carbon revealedgood surface characteristics with large pore volumes [K. S.Triantafyllidis, E. A. Deliyanni, Desulfurization of diesel fuels:Adsorption of 4,6-DMDBT on different origin and surface chemistrynanoporous activated carbons, Chem. Eng. J. 236 (2014) 406-414]. Inaddition, an activated carbon support can be treated in an acidic or abasic solution to generate a surface modified support that has activeadsorptive sites [C. Y. Yin, M. K. Aroua, W. M. Daud, Review ofmodifications of activated carbon for enhancing contaminant uptakes fromaqueous solutions, Sep. Purif. Technol. 52 (2007) 403-415]. In a recentstudy, an activated carbon support has been impregnated with Pd, Al, andFe. The resulting adsorbent revealed promising results in an adsorptivedesulfurization process [A. Lopes, A. Scheer, G. Silva, C. Yamamoto,Pd-Impregnated activated carbon and treatment acid to remove sulfur andnitrogen from diesel, Materia (Rio Janeiro) 21 2016 407-415; S. A.Ganiyu, K. Alhooshani, K. O. Sulaiman, M. Qamaruddin, I. A. Bakare, A.Tanimu, T. A. Saleh, Influence of aluminium impregnation on activatedcarbon for enhanced desulfurization of DBT at ambient temperature: Roleof surface acidity and textural properties, Chem. Eng. J. 303 (2016)489-500; J. X. Guo, S. Shu, X. L. Liu, X. J. Wang, H. Q. Yin, Y. H. Chu,Influence of Fe loadings on desulfurization performance of activatedcarbon treated by nitric acid, Environ. Technol. 3330 (2016) 1-11].

In view of the forgoing, one objective of the present invention is toprovide a sulfur removal system that utilizes an adsorbent toeffectively remove sulfur compounds via an adsorptive desulfurizationprocess at room temperature and atmospheric pressure. The adsorbentincludes cobalt and copper on an activated carbon support.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure relates to a sulfurremoval system including i) a first reactor including a) a first vesselhaving a first internal cavity with a first adsorbent bed that containsa first adsorbent, b) a first inlet located proximal to a bottom of thefirst vessel, c) a first outlet located proximal to a top of the firstvessel, ii) a second reactor including a second vessel having a secondinlet, a second outlet, and a second internal cavity with a secondadsorbent bed that contains a second adsorbent, wherein the first andthe second adsorbents comprise cobalt and copper on an activated carbonsupport, wherein the first adsorbent bed has a cross-sectional area thatis substantially the same as a cross-sectional area of the first vessel,and wherein the second inlet is fluidly connected to the first outletvia a connecting line.

In one embodiment, the first and the second adsorbents are substantiallythe same.

In one embodiment, the system further includes a lower mesh structurelocated in the first internal cavity and proximal to the bottom of thefirst vessel and an upper mesh structure located in the first internalcavity and proximal to the top of the first vessel, defining the firstadsorbent bed.

In one embodiment, the first adsorbent has a particle size in the rangeof 0.5 to 10 mm, and wherein the lower and the upper mesh structureshave a mesh size of less than 0.5 mm.

In one embodiment, the first reactor is a fluidized-bed reactor.

In one embodiment, the second reactor is a fixed-bed reactor.

In one embodiment, the second inlet is located proximal to a top of thesecond vessel and the second outlet is located proximal to a bottom ofthe second vessel.

In one embodiment, the second inlet is located proximal to a bottom ofthe second vessel and the second outlet is located proximal to a top ofthe second vessel.

In one embodiment, the system further includes a liquid reservoirlocated upstream of and fluidly connected to the first inlet via asolvent line, wherein the liquid reservoir is configured to deliver asolvent to the first and the second internal cavities to regenerate thefirst and the second adsorbents.

According to a second aspect, the present disclosure relates to a methodof desulfurizing a sulfur-containing hydrocarbon stream with the sulfurremoval system, involving i) delivering the sulfur-containinghydrocarbon stream to the first inlet and contacting thesulfur-containing hydrocarbon stream with the first adsorbent to form apartially desulfurized hydrocarbon stream, ii) delivering the partiallydesulfurized hydrocarbon stream to the second inlet and contacting thepartially desulfurized hydrocarbon stream with the second adsorbent toform a desulfurized hydrocarbon stream.

In one embodiment, the sulfur-containing hydrocarbon stream is contactedwith the first adsorbent at a temperature of 15 to 35° C. and a pressureof 0.9 to 1.1 atm.

In one embodiment, the partially desulfurized hydrocarbon stream iscontacted with the second adsorbent at a temperature of 15 to 35° C. anda pressure of 0.9 to 1.1 atm.

In one embodiment, the sulfur-containing hydrocarbon stream comprises atleast one sulfur compound selected from the group consisting of athiophene, a benzothiophene, a dibenzothiophene, a methylbenzothiophene, a methyl dibenzothiophene, and a dimethyldibenzothiophene.

In one embodiment, a concentration of sulfur compounds in thesulfur-containing hydrocarbon stream is at least 50 ppm, and wherein aconcentration of sulfur compounds in the desulfurized hydrocarbon streamis no more than 5 ppm.

In one embodiment, the sulfur removal system further includes a liquidreservoir located upstream of and fluidly connected to the first inletvia a solvent line, and the method further involves delivering a solventto the first inlet to regenerate the first adsorbent and the secondinlet to regenerate the second adsorbent.

In one embodiment, the first adsorbent is regenerated within the firstreactor and the second adsorbent is regenerated within the secondreactor.

In one embodiment, the method further involves delivering an inert gasto the first inlet to evaporate the solvent, after delivering thesolvent.

In one embodiment, the inert gas is nitrogen gas with a temperature inthe range of 150 to 350° C., which is delivered with a flow rate of 0.02to 5 L/min.

According to a third aspect, the present disclosure relates to a methodof making an adsorbent, which comprises cobalt and copper on anactivated carbon support. The method involves i) mixing activated carbonparticles with an aqueous solution comprising at least one of ethanol,diethylene glycol, and sodium diacetate to form a first suspension, ii)mixing a cobalt-containing solution with the first suspension andrefluxing to form cobalt-containing activated carbon particles, iii)filtering and drying the cobalt-containing activated carbon particlesand mixing the same with the aqueous solution to form a secondsuspension, iv) mixing and refluxing a copper-containing solution withthe second suspension to form the adsorbent.

In one embodiment, the method further involves i) isothermally heating arubber at a temperature of 250 to 550° C. to form a char, ii) treatingthe char with an oxidizing agent to remove organic impurities, iii)isothermally heating the char at a temperature of 400 to 900° C., iv)treating the char with an acid solution to form the activated carbonparticles, prior to mixing the activated carbon particles with theaqueous solution.

In one embodiment, the cobalt-containing solution is cobalt acetatedissolved in deionized water.

In one embodiment, the copper-containing solution is copper nitratedissolved in deionized water.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1A is a schematic of a sulfur removal system with a first and asecond reactor located in series to one another.

FIG. 1B is a top-view of a lower or an upper mesh structure of the firstor the second reactor.

FIG. 1C is a schematic of a sulfur removal system with a fluidized-bedreactor.

FIG. 1D is a schematic of a sulfur removal system with a fixed-bedreactor.

FIG. 1E is a schematic of a sulfur removal system with a fixed-bedreactor, and a liquid reservoir for regenerating an adsorbent present inthe fixed-bed reactor.

FIG. 1F is a schematic of a sulfur removal system with a fluidized-bedreactor and a fixed-bed reactor located in series to one another.

FIG. 1G is a schematic of a sulfur removal system with a fluidized-bedreactor and a fixed-bed reactor located in series to one another, and aliquid reservoir for regenerating a first and a second adsorbent presentin the fluidized-bed reactor and the fixed-bed reactor.

FIG. 2 represents a rate of adsorption of sulfur compounds present in asulfur-containing stream, when exposed to an adsorbent that includescobalt and copper on an activated carbon support, at different contacttime.

FIG. 3 represents breakthrough curves of compounds present in asulfur-containing stream, when exposed to an adsorbent that includescobalt and copper on an activated carbon support.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views.

Referring to FIG. 1A, according to a first aspect, the presentdisclosure relates to a sulfur removal system 100 that includes a firstreactor 102 having a first vessel 104. The first vessel has a firstadsorbent bed 106 that contains a first adsorbent.

In a preferred embodiment, the first reactor 102 includes a cylindricalvessel that is vertically oriented, wherein a sulfur-containinghydrocarbon stream, which is preferably in a liquid state, enters saidfirst reactor from a bottom end. In another preferred embodiment, thefirst reactor 102 is a fluidized-bed reactor, wherein thesulfur-containing hydrocarbon stream is passed through the firstadsorbent present in the first adsorbent bed at high velocity to suspendthe first adsorbent, whereby at least a portion of sulfur compoundspresent in the sulfur-containing hydrocarbon stream are absorbed by thefirst adsorbent.

The term “first vessel” as used herein refers to a compartment having afirst internal cavity that is configured to contain a solid, a liquid,and/or a gas at various temperatures and pressures. In a preferredembodiment, the first vessel 104 is made of a material that canwithstand a corrosive environment provided by sulfur compounds presentin the sulfur-containing hydrocarbon stream. For example, in oneembodiment, the first vessel is made of quartz or a plastic composite(e.g. epoxy composite, vinyl ester, etc.). In an alternative embodiment,the first vessel is made of a metal or a metal alloy such as stainlesssteel, nickel steel, chromium steel, aluminum, aluminum alloy, copperand copper alloys, titanium, and the like. Accordingly, an inner surfaceof the first vessel is coated with a polymeric liner (e.g. an epoxyliner), quartz, or Pyrex® to prevent corrosion. Alternatively, the innersurface of the first vessel may be coated with a ceramic material suchas silica, alumina, or borides, carbides, nitrides, and/or oxides oftransition metals selected from the group consisting of Al, Si, Sc, Ti,V, Cr, Zr, Nb, Mo, Hf, Ta, and Th, for example, hafnium diboride (HfB₂),zirconium diboride (ZrB₂), hafnium nitride (HfN), zirconium nitride(ZrN), titanium carbide (TiC), titanium nitride (TiN), thorium dioxide(ThO₂), tantalum carbide (TaC), and composites thereof. Although thematerials used to construct the first vessel are not meant to belimiting and various other materials may also be used.

In a preferred embodiment, the first vessel 104 is vertically orientedwith a cylindrical geometry with a first and a second end separated by aside wall along a longitudinal axis, and a height in the range of 0.2 to10 m, preferably 0.5 to 9 m, preferably 1 to 8 m, preferably 3 to 7 m,preferably 4 to 6 m, and a diameter in the range of 1 to 200 cm,preferably 10 to 180 cm, preferably 20 to 150 cm, preferably 30 to 140cm, preferably 40 to 130 cm, preferably 50 to 120 cm, preferably 60 to110 cm, preferably 70 to 105 cm, preferably 80 to 100 cm. The firstvessel 104 may have a volume in the range of 0.1-100,000 L, preferably1-50,000 L, preferably 10-40,000 L, preferably 100-30,000 L, preferably500-20,000 L, preferably 1,000-10,000 L, preferably 2,000-5,000 L. Thefirst vessel may also have other geometries such as rectilinear orrectangular, which may preferably be vertically oriented.

The first adsorbent bed 106 is located inside the first internal cavity,and the first adsorbent bed contains the first adsorbent. Across-sectional area of the first adsorbent bed 106 is substantially thesame as a cross-sectional area of the first vessel 104. Accordingly, inone embodiment, the first vessel 104 is a vertically orientedcylindrical vessel having a circular cross-section with a diameter inthe range of 1 to 200 cm, preferably 10 to 180 cm, preferably 20 to 150cm, preferably 30 to 140 cm, preferably 40 to 130 cm, preferably 50 to120 cm, preferably 60 to 110 cm, preferably 70 to 105 cm, preferably 80to 100 cm, wherein the first adsorbent bed 106 also has a circularcross-section with a diameter in the range of 1 to 200 cm, preferably 10to 180 cm, preferably 20 to 150 cm, preferably 30 to 140 cm, preferably40 to 130 cm, preferably 50 to 120 cm, preferably 60 to 110 cm,preferably 70 to 105 cm, preferably 80 to 100 cm. In view of thisembodiment, the first adsorbent, which is present in the first adsorbentbed 106, cannot move along the longitudinal axis of the first vessel.Accordingly, the first vessel is made of a singular construction andthere is no inner wall within the first vessel, e.g. a wall that issubstantially parallel to the longitudinal axis of the first vessel andis configured to segregate a portion of the first adsorbent from therest. Therefore, the first adsorbent is present in the first adsorbentbed and moves within the first adsorbent bed. With that being said, thefirst adsorbent may preferably not be found anywhere else in the firstvessel, except in the first adsorbent bed. For example, the first vesseldoes not include a separating zone and/or a settling zone as in thepatent reference GB 1,495,586. In another embodiment, thesulfur-containing hydrocarbon stream is evenly distributed to the bottomof the first adsorbent bed so that the sulfur-containing hydrocarbonstream is evenly contacted with the first adsorbent present in the firstadsorbent bed. For example, in one embodiment, the sulfur-containinghydrocarbon stream is evenly distributed when a distributer (e.g. ashower head flow distributor) is disposed in the first inlet and insidethe vessel. Accordingly, the sulfur-containing hydrocarbon stream ispreferably evenly contacted with the first adsorbent present in thefirst adsorbent bed.

The term “substantially the same” as used in this disclosure refers toembodiments wherein a quantity differs by no more than 1%, preferably byno more than 0.5%. For example, the phrase “a cross-sectional area ofthe first adsorbent bed is substantially the same as a cross-sectionalarea of the first vessel”, means that the cross-sectional area of thefirst adsorbent bed differs by no more than 1%, preferably by no morethan 0.5% of the cross-sectional area of the first vessel.

In one embodiment, a height of the first adsorbent bed 106 is 20% to95%, preferably 30% to 90%, preferably 40% to 85%, preferably 50% to 80%relative to the height of the first vessel, which is in the range of 0.2to 10 m, preferably 0.5 to 9 m, preferably 1 to 8 m, preferably 3 to 7m, preferably 4 to 6 m. In some embodiments, the height of the firstadsorbent bed is less than 50%, for example in the range of 20% to 50%,preferably 25% to 45%, preferably 30% to 40% relative to the height ofthe first vessel, and a plurality of first adsorbent beds (e.g. two,three, four, but no more than ten) are arranged in the first vessel. Inthe above embodiments, the first adsorbent bed is fixed inside the firstvessel (i.e. the first adsorbent bed does not move along thelongitudinal axis of the first vessel).

In one embodiment, the first reactor 102 further includes a lower meshstructure 144 located in the first internal cavity and proximal to thebottom of the first vessel 104 and an upper mesh structure 142 locatedin the first internal cavity and proximal to the top of the first vessel104, defining the first adsorbent bed 106. Accordingly, the height ofthe first adsorbent bed is defined as a distance between the lower andthe upper mesh structures. Preferably, each of the lower and the uppermesh structures has a planar axis and the lower and the upper meshstructures secured inside the first vessel 104 such that the planar axisof each is substantially perpendicular to the longitudinal axis of thefirst vessel 104. In some embodiments, the lower and the upper meshstructures are tilted such that an angle between the planar axis of eachof the lower and the upper mesh structures and the longitudinal axis ofthe first vessel is in the range of 80 to 1000, preferably 82 to 980,preferably 84 to 960, preferably 86 to 940, preferably 88 to 920. In apreferred embodiment, the lower and the upper mesh structures have thesame diameter as that of the first vessel, when the planar axis of eachof the mesh structures is perpendicular with the longitudinal axis ofthe first vessel (as shown in FIG. 1A). In another embodiment, theplanar axis of each of the lower and the upper mesh structures form anangle in the range of 80 to 1000, preferably 82 to 980, preferably 84 to960, preferably 86 to 940, preferably 88 to 920 with the longitudinalaxis of the first vessel, wherein, each mesh structure has a largerdiameter than a diameter of the first vessel.

Each of the lower and the upper mesh structures are configured to securethe first adsorbent in place within the first internal cavity, therebyallowing the sulfur-containing hydrocarbon stream to pass through thefirst adsorbent bed. In view of that, in one embodiment, the firstadsorbent has a particle size in the range of 0.5 to 10 mm, preferably 1to 8 mm, preferably 1.2 to 6 mm, preferably 1.4 to 5 mm, preferably 1.5to 4 mm, and the lower and the upper mesh structures have a mesh size ofless than 0.5 mm. In a preferred embodiment, a mesh size of the lowerand the upper mesh structures is at least 5%, preferably at least 10%smaller than a size of the smallest adsorbent particle found in thefirst adsorbent. For example, if the smallest adsorbent particle foundin the first adsorbent is 1 mm, the mesh size in the lower and the uppermesh structures is preferably 0.95 mm, more preferably 0.9 mm. The term“mesh size” as used herein refers to the size of the holes (i.e. meshes)present in the mesh structures measured via ASTM E11:01. A top viewcross-section of each of the lower and the upper mesh structure isdepicted in FIG. 1B. Since the mesh size of the mesh structures issmaller than the particle size of the first adsorbent, the firstadsorbent is secured in the first adsorbent bed.

The first reactor 102 further includes a first inlet 108 locatedproximal to the bottom of the first vessel 104 and a first outlet 110located proximal to the top of the first vessel 104. The first inlet andthe first outlet are configured as passages for loading and unloadingthe first vessel. The first inlet 108 is preferably secured parallel tothe longitudinal axis of the first vessel, whereas the first outlet 110may preferably be secured perpendicular (as shown in FIG. 1A) orparallel to the longitudinal axis of the first vessel (as shown in FIG.1F). In another embodiment, an angle between a longitudinal axis of thefirst outlet and that of the first vessel is in the range of 5 to 850,preferably 15 to 750, preferably 25 to 650, preferably to 550,preferably about 45°.

The phrase “proximal to the bottom of the first vessel” as used hereinrefers to a region of the first vessel that is located less than 20%,preferably less than 15%, preferably less than 10%, preferably less than5% of the height of the first vessel, when measured from the bottom ofthe first vessel, with 0%/a being the bottom and 100% being the top ofthe first vessel. Accordingly, the phrase “proximal to the top of thefirst vessel” as used herein refers to a region of the first vessel thatis located less than 20%, preferably less than 15%, preferably less than100%, preferably less than 5% of the height of the first vessel, whenmeasured from the top of the first vessel, with 0%/a being the top and100% being the bottom of the first vessel.

In one embodiment, the first inlet 108 and the first outlet 110 aresubstantially the same, wherein each is a cylindrical port having aninternal diameter in the range of 1-100 mm, preferably 5-80 mm,preferably 10-70 mm, preferably 15-60 mm, more preferably 20-50 mm.Preferably, the first inlet 108 and the first outlet 110 are made of amaterial that can withstand a corrosive environment provided by sulfurcompounds present in the sulfur-containing hydrocarbon stream that isdelivered to the first vessel. For example, in one embodiment, the firstinlet and the first outlet are made of quartz or a plastic composite(e.g. epoxy composite, vinyl ester, etc.). In an alternative embodiment,the first inlet and the first outlet are made of a metal or a metalalloy such as stainless steel, nickel steel, chromium steel, aluminum,aluminum alloy, copper and copper alloys, titanium, and the like.Accordingly, an inner surface of the first inlet and the first outletare coated with a polymeric liner (e.g. an epoxy liner), quartz, orPyrex® to prevent corrosion. Other than the first inlet and the firstoutlet designed to allow ingress and egress, the first vessel may besealed to prevent any leakage.

The sulfur removal system 100 further includes a second reactor 114 witha second vessel 116. The second vessel has a second adsorbent bed 118that contains a second adsorbent. Preferably, the second reactor 114 isa cylindrical vessel that is vertically or horizontally oriented,wherein a partially desulfurized hydrocarbon stream, which is preferablyin a liquid state, enters the reactor from a bottom or a top end (whenthe reactor is vertically oriented) or from a left or a right end (whenthe reactor is horizontally oriented). In a preferred embodiment, thesecond reactor 114 is a fixed-bed reactor, wherein the partiallydesulfurized hydrocarbon stream is passed through the second adsorbentpresent in the second adsorbent bed 118, to adsorb at least a portion ofsulfur compounds present in the partially desulfurized hydrocarbonstream.

The second vessel 116 refers to a compartment having a second internalcavity, configured to contain a solid, a liquid, and/or a gas at varioustemperatures and pressures. In a preferred embodiment, specification ofthe second vessel 116 such as sizing and the type of materials used formanufacturing the second vessel are substantially the same as that ofthe first vessel 104. Although in some embodiments, a sizing and/or thetype of materials of the second vessel is different than that of thefirst vessel.

In one embodiment, a cross-sectional area of the second adsorbent bed118 is substantially the same as a cross-sectional area of the secondvessel 116. Accordingly, in one embodiment, the second vessel 116 is avertically oriented cylindrical vessel having a circular cross-sectionwith a diameter in the range of 1 to 200 cm, preferably 10 to 180 cm,preferably to 150 cm, preferably 30 to 140 cm, preferably 40 to 130 cm,preferably 50 to 120 cm, preferably 60 to 110 cm, preferably 70 to 105cm, preferably 80 to 100 cm, wherein the second adsorbent bed also has acircular cross-section with a diameter in the range of 1 to 200 cm,preferably 10 to 180 cm, preferably 20 to 150 cm, preferably 30 to 140cm, preferably 40 to 130 cm, preferably 50 to 120 cm, preferably 60 to110 cm, preferably 70 to 105 cm, preferably 80 to 100 cm. In anotherembodiment, the second adsorbent bed has other geometries including, butnot limited to a hollow tube, a pipe, a duct, etc. In a preferredembodiment, the second adsorbent is stationary in the second adsorbentbed 118, and only a fluid, preferably in liquid state, is passed throughthe second adsorbent bed.

In one embodiment, a height (or length in case the second vessel ishorizontally oriented) of the second adsorbent bed is 20% to 95%,preferably 30% to 90%, preferably 40% to 85%, preferably 50% to 80%relative to the height/length of the second vessel, which is in therange of 0.2 to 10 m, preferably 0.5 to 9 m, preferably 1 to 8 m,preferably 3 to 7 m, preferably 4 to 6 m. In one embodiment, the secondadsorbent bed 118 is fixed inside the second vessel 116 (i.e. the secondadsorbent bed does not move along the longitudinal axis of the secondvessel), although the second adsorbent bed may also move along thelongitudinal axis of the second vessel. In some embodiments, theheight/length of the second adsorbent bed is less than 50%, for examplein the range of 20% to 50%, preferably 25% to 45%, preferably 30% to 40%relative to the height/length of the second vessel, and a plurality ofsecond adsorbent beds (e.g. two, three, four, but no more than ten) arearranged in the second vessel.

In one embodiment, at least 50%/a, preferably at least 60%, preferablyat least 70%, preferably at least 80%/a, preferably at least 85%, but nomore than 90% of the total volume of the first adsorbent bed 106 isfilled with the first adsorbent. In another embodiment, 100% of thetotal volume of the second adsorbent bed 118 is filled with the secondadsorbent, wherein the volume of the second adsorbent bed is at least50%, preferably at least 60%, preferably at least 70%, preferably atleast 80%, preferably at least 85%, but no more than 90% of the totalvolume of the second vessel 116.

In one embodiment, the second reactor 114 further includes a secondlower mesh structure 146 located in the second internal cavity andproximal to the bottom of the second vessel 116 and a second upper meshstructure 148 located in the second internal cavity and proximal to thetop of the second vessel 116, defining the second adsorbent bed 118.Accordingly, the height of the second adsorbent bed is defined as adistance between the lower and the upper mesh structures. Preferably,the second lower and the second upper mesh structures are substantiallythe same as that of the lower and the upper mesh structures, as depictedin FIG. 1B.

The second reactor 114 further includes a second inlet 120 and a secondoutlet 122. The second inlet and the second outlet are configured aspassages for loading and unloading the second vessel. The second inlet120 and the second outlet 122 are preferably secured parallel (as shownin FIG. 1A) or perpendicular to the longitudinal axis of the secondvessel 116. In another preferred embodiment, the second inlet is securedparallel to the longitudinal axis of the second vessel, and the secondoutlet is secured such that an angle between a longitudinal axis of thesecond outlet and that of the second vessel is in the range of 5 to 850,preferably 15 to 75°, preferably 25 to 650, preferably 35 to 550,preferably about 45°.

In a preferred embodiment, the second vessel 116 is vertically oriented,wherein the second inlet 120 is located proximal to the top of thesecond vessel and the second outlet 122 is located proximal to thebottom of the second vessel. In view of this embodiment, a liquid stream(i.e. the partially desulfurized hydrocarbon stream) has a downward flowdirection inside the second vessel. In an alternative embodiment, thesecond vessel is vertically oriented, wherein the second inlet islocated proximal to the bottom of the second vessel and the secondoutlet is located proximal to the top of the second vessel. In view ofthis embodiment, a liquid stream (i.e. the partially desulfurizedhydrocarbon stream) has an upward flow direction inside the secondvessel.

In one embodiment, the second inlet 120 and the second outlet 122 aresubstantially the same, wherein each is a cylindrical port having aninternal diameter in the range of 1-100 mm, preferably 5-80 mm,preferably 10-70 mm, preferably 15-60 mm, more preferably 20-50 mm. In apreferred embodiment, specification of the second inlet 120 and thesecond outlet 122 such as sizing and the type of materials used formanufacturing are substantially the same to that of the first inlet 108and the first outlet 110. Although in another embodiment, the sizingand/or the type of materials of the second inlet and the second outletis different than that of the first inlet and the first outlet. Otherthan the second inlet and the second outlet designed to allow ingressand egress, the second vessel may be sealed to prevent any leakage.

The second inlet 120 is fluidly connected to the first outlet 110 via aconnecting line 138. The connecting line 138 refers to a tubular channelconfigured to fluidly connect the first outlet 110 to the second inlet120. Preferably, the connecting line 138 is made of a metal or a metalalloy with an anti-corrosive plastic liner or a ceramic liner (e.g.alumina). In one embodiment, a diameter of the connecting line is in therange of 1-100 mm, preferably 5-80 mm, preferably 10-70 mm, preferably15-60 mm, more preferably 20-50 mm, relative to the diameter of thefirst outlet and the second inlet, which is in the range of 1-100 mm,preferably 5-80 mm, preferably 10-70 mm, preferably 15-60 mm, morepreferably 20-50 mm.

Each of the first and the second vessels further includes a plurality ofbaffles 112 secured to the inner wall of the first and the secondvessels (as depicted in FIG. 1A). In a preferred embodiment, the baffles112 are equally spaced apart in a zigzag arrangement (as shown in FIG.1A). Having the baffles with a zigzag arrangement may provide a longerresidence time of a sulfur-containing stream inside the first and thesecond vessels, when compared to an embodiment where the baffles are notpresent. In another embodiment, the baffles are randomly arranged withinthe vessel. Preferably, each baffle has a planar axis and is secured tothe inner wall of each of the first and the second vessel such that theplanar axis of each baffle is substantially perpendicular to thelongitudinal axis of each of the first vessel and the second vessel. Insome embodiments, the baffles are tilted such that an angle between theplanar axis of each baffle and the longitudinal axis of each vessel isin the range of 70 to 110°, preferably 80 to 100°, preferably 85 to 95°.Preferably, the angle between the planar axis of each baffle and thelongitudinal axis of each vessel is no less than 60° and no more than120°.

In one embodiment, the sulfur removal system 100 further includes ahydrocarbon reservoir 124 located upstream of and fluidly connected tothe first inlet 108 via a feed line 134 and optionally a first pump 130.Accordingly, the sulfur-containing hydrocarbon stream can be deliveredto the first inlet 108 via the feed line 134 and optionally the firstpump 130. Alternatively, the sulfur-containing hydrocarbon stream may bedelivered to the first inlet 108 from an upstream processing plant e.g.a cracking tower of a refinery. Alternatively, the sulfur-containinghydrocarbon stream may be delivered directly from an offshore or anonshore oil well.

In one embodiment, the feed line 134 is a tubular channel that isconfigured to deliver the sulfur-containing hydrocarbon stream 134 s tothe first inlet 108 of the first vessel 104. Preferably, the feed lineis made of a metal or a metal alloy with an anti-corrosive plastic lineror a ceramic liner (e.g. alumina). In one embodiment, a diameter of thefeed line is in the range of 1-100 mm, preferably 5-80 mm, preferably10-70 mm, preferably 15-60 mm, more preferably 20-50 mm, relative to thediameter of the first inlet, which is in the range of 1-100 mm,preferably 5-80 mm, preferably 10-70 mm, preferably 15-60 mm, morepreferably 20-50 mm.

In another embodiment, the sulfur removal system 100 further includes aproduct tank 128 located downstream of and fluidly connected to thesecond outlet 122 via a product line 140. Preferably, the specificationof the product line 140 is substantially the same as that of the feedline 134.

In one embodiment, the sulfur removal system 100 further includes aliquid reservoir 126 located upstream of and fluidly connected to thefirst inlet 108 via a solvent line 136 and optionally a second pump 132.Accordingly, a solvent can be delivered to the first inlet 108 via thesolvent line 136 and optionally the second pump 132. In one embodiment,the liquid reservoir 126 is coated with an anti-corrosive liner toprevent surface oxidation in the liquid reservoir. For example, in oneembodiment, the liquid reservoir is made of quartz, a metal, or a metalalloy such as stainless steel, nickel steel, chromium steel, aluminum,aluminum alloy, copper and copper alloys, titanium, and the like.Accordingly, an inner surface of the first vessel is preferably coatedwith a polymeric liner (e.g. an epoxy liner), quartz, or Pyrex® toprevent corrosion. The liquid reservoir 126 is configured to contain asolvent and deliver the solvent to the first and the second internalcavities to regenerate the first and the second adsorbents.

The solvent line 136 is a tubular channel configured to fluidly connectthe liquid reservoir 126 to the first inlet 108. Preferably, the solventline 136 is made of a metal or a metal alloy with an anti-corrosiveplastic liner or a ceramic liner (e.g. alumina). In one embodiment, adiameter of the solvent line is in the range of 1-100 mm, preferably5-80 mm, preferably 10-70 mm, preferably 15-60 mm, more preferably 20-50mm, relative to the diameter of the first inlet 108, which is in therange of 1-100 mm, preferably 5-80 mm, preferably 10-70 mm, preferably15-60 mm, more preferably 20-50 mm.

In one embodiment, the solvent is at least one organic solvent selectedfrom the group consisting of methanol, toluene, tetrahydrofuran, aceticacid, acetone, acetonitrile, butanol, dichloromethane, chloroform,chlorobenzene, dichloroethane, diethylene glycol, diethyl ether,dimethoxy-ethane, dimethyl-formamide, dimethyl sulfoxide, ethanol, ethylacetate, ethylene glycol, heptane, hexamethylphosphoramide,hexamethylphosphorous triamide, methanol, methyl t-butyl ether,methylene chloride, pentane, cyclopentane, hexane, cyclohexane, benzene,dioxane, propanol, isopropyl alcohol, pyridine, triethyl amine,propandiol-1,2-carbonate, ethylene carbonate, propylene carbonate,nitrobenzene, formamide, 7-butyrolactone, benzyl alcohol,n-methyl-2-pyrrolidone, acetophenone, benzonitrile, valeronitrile,3-methoxy propionitrile, dimethyl sulfate, aniline, n-methylformamide,phenol, 1,2-dichlorobenzene, tri-n-butyl phosphate, ethylene sulfate,benzenethiol, dimethyl acetamide, N,N-dimethylethaneamide,3-methoxypropionnitrile, diglyme, cyclohexanol, bromobenzene,cyclohexanone, anisole, diethylformamide, 1-hexanethiol, ethylchloroacetate, 1-dodecanthiol, di-n-butylether, dibutyl ether, aceticanhydride, m-xylene, o-xylene, p-xylene, morpholine, diisopropyletheramine, diethyl carbonate, 1-pentandiol, n-butyl acetate, and1-hexadecanthiol. The solvent may have a boiling point of at least 60°C., preferably at least 70° C., more preferably at least 80° C.Preferably, the solvent is capable of dissolving sulfur compounds,without negatively affecting (e.g. poisoning) the first and the secondadsorbents. Preferably, the solvent comprises methanol and/or toluene.

Referring now to FIG. 1C, in one embodiment, the sulfur removal systemonly includes a fluidized-bed reactor 102, which is connected to thehydrocarbon reservoir 124 via the feed line 134, the first pump 130, afirst valve 131, and a flow meter 133. A desulfurized hydrocarbonstream, which egresses the fluidized-bed reactor 102 may further bedelivered to the product tank 128 via the product line 140.

Referring now to FIG. 1D, in one embodiment, the sulfur removal systemonly includes a fixed-bed reactor 114, which is connected to ahydrocarbon reservoir 124 via a feed line 134, a first pump 130, a firstvalve 131, and a flow meter 133. An effluent desulfurized stream, whichegresses the fixed-bed reactor 102 is delivered to a product tank 128via a product line 140, and a third valve 139. In another embodiment, aliquid reservoir 126 is located upstream of and fluidly connected to thefixed-bed reactor 114 via a solvent line 136, a second pump 132, and asecond valve 135 (as depicted in FIG. 1E). Accordingly, the first valve131 is closed and the second valve 135 is opened allowing a solvent topass through the reactor to regenerate the adsorbent present in thereactor 114 by removing sulfur compounds from the surface of theadsorbent present in the reactor. A contaminated solvent, which egressesthe reactor, may be collected in a container located downstream of thereactor. In one embodiment, a sample of the solvent is delivered to achemical composition analyzer 145 (e.g. a gas chromatograph equippedwith a sulfur chemiluminescence detector) via the product line 140 and afourth valve 137. Sampling the solvent is preferred, because atermination of adsorbent regeneration may be determined viainstantaneous detection of the contaminated solvent. In view of that,once a concentration of sulfur compounds drops below a predeterminedvalue (e.g. less than 5 ppm, preferably less than 1 ppm), the secondvalve 135 is closed and the first valve 131 is opened, allowing asulfur-containing stream to flow through the reactor 114.

Referring now to FIG. 1F, in one embodiment, the sulfur removal systemincludes a fluidized-bed reactor 102 and a fixed-bed reactor 114 locatedin series, wherein an inlet of the fixed-bed reactor (i.e. the secondinlet) is located proximal to the top of the fixed-bed reactor 114.

Referring now to FIG. 1G, in one embodiment, the sulfur removal systemincludes a fluidized-bed reactor 102 and a fixed-bed reactor 114 locatedin series. A liquid reservoir 126 is located upstream of and fluidlyconnected to the fluidized-bed reactor 102 and the fixed-bed reactor 114via separate solvent lines 136, a second pump 132, and separate secondvalves 135 (as depicted in FIG. 1G). Accordingly, the first valve 131 isclosed and the second valves 135 are opened allowing a solvent to passthrough both the fluidized-bed reactor 102 and the fixed-bed reactor 114to regenerate the first and the second adsorbent present in bothreactors. In view of that, in one embodiment, a fifth 151, a sixth 155,and a seventh valve 157 are located on the connecting line (as depictedin FIG. 1G). Preferably, the fifth valve 151 is closed, while both thesixth valve 155 and the seventh valves 157 are opened, allowing thefirst and the second adsorbents present in the fluidized-bed reactor 102and the fixed-bed reactor 114 to be individually treated/regenerated.

Both the first and the second adsorbents include cobalt and copper on anactivated carbon support to absorb at least a portion of sulfurcompounds present in the sulfur-containing hydrocarbon stream and thepartially desulfurized hydrocarbon stream that are passed through thefirst and the second adsorbents. Exemplary of such sulfur compoundsinclude, but are not limited to mercaptans, sulfides, disulfides,polysulfides, thiols, thioethers, thioesters, thioacetals, sulfoxides,sulfones, thiosulfonates, sulfimides, sulfoximides, sulfonediimines,s-nitrosothiols, sulfur halides, thioketones, thioaldehydes,thiocarbonyls, sulfur oxides, thiocarboxylic acids, thioamides, sulfonicacid, sulfinic acid, sulfenic acids, sulfonium, oxosulfonium,sulfuranes, and persulfuranes.

Preferably, the first and the second adsorbents adsorb sulfur compoundspresent in the sulfur-containing hydrocarbon stream and the partiallydesulfurized hydrocarbon stream, and may not involve ahydro-desulfurization reaction whereby sulfur is removed from an organicsulfur compound via a catalytic chemical reaction in the presence ofhydrogen. Accordingly, the term “desulfurization” as used in thisdisclosure refers to a process of removing sulfur compounds from astream (e.g. a sulfur-containing hydrocarbon stream) via an adsorptiveprocess, and does not refer to a removal of sulfur from an organicsulfur compound via a catalytic chemical reaction. Furthermore, the term“desulfurized hydrocarbon stream” as used in this disclosure refers to astream that is substantially free from sulfur compounds that are removedvia an adsorptive desulfurization process.

In a preferred embodiment, an average particle size of the first and thesecond adsorbents are substantially the same, wherein each is in therange of 0.5 to 10 mm, preferably 0.75 to 9 mm, preferably 0.8 to 8 mm,preferably 0.85 to 7 mm, preferably 0.9 to 6 mm, preferably 0.95 to 5mm, preferably 1 to 4 mm, preferably 1.5 to 3 mm, preferably 1.75 to 2mm.

In a preferred embodiment, a composition of the first and the secondadsorbents are substantially the same, wherein each includes cobalt witha weight percent in the range of 1 to 3 wt %, preferably 1.5 to 2.5 wt%, preferably about 2 wt %, and copper with a weight percent in therange of 1 to 5 wt %, preferably 2 to 4 wt %, preferably about 3 wt %,with each weight percentile being relative to the total weight of eachof the adsorbents. In an alternative embodiment, the first and thesecond adsorbents are different. Accordingly the difference between thefirst and the second adsorbents relates to a weight percent of cobaltand copper. For example, in one embodiment, a weight percent of cobaltin the first adsorbent is in the range of 1 to 3 wt %, preferably 1.5 to2.5 wt %, preferably about 2 wt %, and a weight percent of copper in thefirst adsorbent is in the range of 1 to 5 wt %, preferably 2 to 4 wt %,preferably about 3 wt %, whereas a weight percent of cobalt in thesecond adsorbent is in the range of 1 to 5 wt %, preferably 3 to 4 wt %,preferably about 3.5 wt %, and a weight percent of copper in the firstadsorbent is in the range of 1 to 5 wt %, preferably 3 to 4 wt %,preferably about 3.5 wt %, relative to the total weight of each of theadsorbents.

In one embodiment, the first and the second adsorbents further includeone or more metals selected from nickel, copper, zinc, cobalt, andmolybdenum and/or their oxides and mixtures thereof.

The activated carbon support of each of the adsorbents may be present inthe form of a granular activated carbon or a powdered activated carbon.The granular activated carbon may have attributes, such as a pore volumeof 0.5-1.0 cm³/g, preferably 0.6-0.95 cm³/g, more preferably 0.7-0.9cm³/g, even more preferably 0.8-0.85 cm³/g; a specific surface area of700 to 1500 m²/g, preferably 1000 to 1450 m²/g, more preferably 1200 to1400 m²/g; and micro-pores (i.e. pores with an average pore diameter of12-30 Å, preferably 13-20 Å, more preferably 14-15 Å), meso-pores (i.e.pores with an average pore diameter of 15-50 Å, preferably 20-45 Å, morepreferably 25-40 Å), and/or macro-pores (i.e. pores with an average porediameter of at least 50 Å, preferably at least 60 Å).

In one embodiment, the granular activated carbon is recyclable. Inanother embodiment, the granular activated carbon does not undergoparticle coagulation therefore a chance of clogging is low. The granularactivated carbon may also remove phenolic compounds andmercury-containing compounds present in a sulfur-containing stream thatdelivers to the first and the second vessels. Further, the granularactivated carbon may also remove or reduce chlorine and/or parasitescontent of the sulfur-containing stream. The powdered activated carbonmay have attributes, such as a pore volume of 0.1-0.5 cm³/g, preferably0.2-0.45 cm³/g, more preferably 0.3-0.4 cm³/g; a specific surface areaof 700 to 1500 m²/g, preferably 1000 to 1450 m²/g, more preferably 1200to 1400 m²/g; and micro-pores (i.e. pores with an average pore diameterof 12-30 Å, preferably 13-20 Å, more preferably 14-15 Å), meso-pores(i.e. pores with an average pore diameter of 15-50 Å, preferably 20-45Å, more preferably 25-40 Å), and/or macro-pores (i.e. pores with anaverage pore diameter of at least 50 Å, preferably at least 60 Å). Thepowdered activated carbon is preferred over granular activated carbon asthe powdered activated carbon has a higher adsorption rate.

In one embodiment, the activated carbon support has a variety ofcapabilities to be appropriate for different purposes of sulfuradsorption. For example, the activated carbon layer may have an iodinenumber of 900 to 2000 mg/g, preferably 1500 to 2000 mg/g; a pore volumeof 0.3 to 0.8 cm³/g, preferably 0.4 to 0.7 cm³/g; a specific surfacearea (BET) of 1000 to 2000 m²/g, preferably 1500 to 1900 m²/g; amicro-pore size of 12 to 20 Å, preferably 14 to 18 Å, and a meso-poresize of 30 to 40 Å, preferably 32 to 38 Å. The term “iodine number” ofan activated carbon is a representative index of the specific surfacearea of the activated carbon.

In a preferred embodiment, the activated carbon support of the firstadsorbent is substantially the same as that of the second adsorbent,each having an iodine number of 900 to 2000 mg/g, preferably 1500 to2000 mg/g; a pore volume of 0.3 to 0.8 cm³/g, preferably 0.4 to 0.7cm³/g; a specific surface area (BET) of 1000 to 2000 m²/g, preferably1500 to 1900 m²/g; a micro-pore size of 12 to 20 Å, preferably 14 to 18Å, and a meso-pore size of 30 to 40 Å, preferably 32 to 38 Å.

In one embodiment, the first and the second adsorbents have irregularshape and geometry, although the first and the second adsorbents mayalso have a cylindrical, a rectilinear, a star-shaped, a conical, apyramidal, a rectangular, a cubical, and/or a ring shape structure.

According to a second aspect, the present disclosure relates to a methodof desulfurizing a sulfur-containing hydrocarbon stream 134 s via thesulfur removal system 100, involving delivering the sulfur-containinghydrocarbon stream 134 s to the first inlet 108 via the feed line 134and contacting the sulfur-containing hydrocarbon stream 134 s with thefirst adsorbent to form a partially desulfurized hydrocarbon stream 138s.

The sulfur-containing hydrocarbon stream 134 s may be delivered from ahydrocarbon reservoir 124 (as shown in FIG. 1A) or directly from anoffshore or an onshore well, which is located upstream of and fluidlyconnected to the first inlet 108 via the feed line 134 and the firstpump 130.

In one embodiment, the sulfur-containing hydrocarbon stream is contactedwith the first adsorbent at a temperature of 15 to 35° C., preferably 20to 30° C., preferably about 25° C., and a pressure of 0.9 to 1.1 atm,preferably 0.95 to 1.05 atm, preferably about 1 atm. In circumstanceswhere a temperature or a pressure of the sulfur-containing hydrocarbonstream falls outside of the above ranges, the temperature and thepressure of the sulfur-containing hydrocarbon stream is first adjustedto be within the ranges mentioned above, and the delivered to the firstinlet 108.

In one embodiment, the sulfur-containing hydrocarbon stream 134 sincludes at least one sulfur compound selected from the group consistingof mercaptans, sulfides, disulfides, polysulfides, thiols, thioethers,thioesters, thioacetals, sulfoxides, sulfones, thiosulfonates,sulfimides, sulfoximides, sulfonediimines, s-nitrosothiols, sulfurhalides, thioketones, thioaldehydes, thiocarbonyls, sulfur oxides,thiocarboxylic acids, thioamides, sulfonic acid, sulfinic acid, sulfenicacids, sulfonium, oxosulfonium, sulfuranes, and persulfuranes. In apreferred embodiment, the sulfur-containing hydrocarbon stream 134 sincludes at least one sulfur compound selected from the group consistingof a thiophene, a benzothiophene, a dibenzothiophene, a methylbenzothiophene, a methyl dibenzothiophene, a dimethyl dibenzothiophene,and a tetrahydrothiophene. More particularly, in another preferredembodiment, the sulfur-containing hydrocarbon stream includes at leastone sulfur compound selected from the group consisting of hydrogensulfide, thiophene, benzothiophene, dibenzo[b,d]thiophene,5-methyl-1-benzothiophene, 4-methyl dibenzo[b,d]thiophene, and4,6-dimethyldibenzo[b,d]thiophene. The sulfur-containing hydrocarbonstream may further contain one or more combustible compounds (alkanes,alkenes, alkynes, cycloalkanes, etc.) having a carbon number in therange of C₁-C₂₀, preferably C₁-C₁₂, more preferably C₁-C₈. Preferably,the sulfur-containing hydrocarbon stream contains less than 5.0 vol %,preferably less than 2.0 vol % of nitrogen and water vapor. Aspreviously discussed, sulfur compounds are removed via an adsorptivedesulfurization process and not a hydro-desulfurization reaction.Therefore, the sulfur-containing hydrocarbon stream preferably does notcontain hydrogen, or in some embodiments, a concentration of hydrogen inthe sulfur-containing hydrocarbon stream is no more than 2.0 vol %,preferably no more than 1.5 vol %, preferably no more than 1.0 vol %,preferably no more than 0.5 vol %, relative to the total volume of thesulfur-containing hydrocarbon stream. Further to the above, thesulfur-containing hydrocarbon stream may include traces amount(preferably less than 0.1 vol %) of argon, helium, and nitrogen oxides(i.e. nitric oxide, nitrous oxide, nitrogen dioxide). Preferably, thesulfur-containing hydrocarbon stream includes at least 70 vol %, morepreferably at least 80 vol %, most preferably at least 90 vol % of thecombustible compounds.

In some embodiments, the sulfur-containing hydrocarbon stream isreceived from an upstream oil well or an upstream refinery processingunit, and has a temperature in a range of 50 to 400° C., preferably 80to 350° C., preferably 100 to 300° C., preferably 120 to 250° C.,preferably 150 to 200° C., and a pressure in the range of 1 to 10 bars,preferably 1.5 to 5 bars, preferably 2 to 4 bars. Accordingly, atemperature of the sulfur-containing hydrocarbon stream is preferablyadjusted to be within the range of 15 to 35° C., preferably 20 to 30°C., preferably about 25° C., and a pressure of the sulfur-containinghydrocarbon stream is preferably adjusted to be within the range of 0.9to 1.5 bars, preferably 0.95 to 1.2 bars, preferably about 1 bar, beforedelivering the sulfur-containing hydrocarbon stream to the first inlet.In an alternative embodiment, only a pressure of the sulfur-containinghydrocarbon stream is adjusted and the temperature is remainedunchanged.

The sulfur-containing hydrocarbon stream is preferably in a liquid phasebefore delivering to the first inlet, even though the sulfur-containinghydrocarbon stream may be present in a binary liquid/gaseous phase. Inview of that, a volume fraction of the liquid phase in the binaryliquid/gaseous phase is at least 0.8, preferably at least 0.85,preferably at least 0.9, preferably at least 0.95, preferably at least0.99.

In one embodiment, a concentration of sulfur compounds in thesulfur-containing hydrocarbon stream is at least 50 ppm, preferably atleast 60 ppm, preferably at least 70 ppm, but no more than 1000 ppm. Inan alternative embodiment, a concentration of sulfur compounds in thesulfur-containing hydrocarbon stream is in the range of 100 to 10,000ppm, preferably 500 to 8,000 ppm, preferably 1,000 to 7,000 ppm,preferably 1,500 to 6,000 ppm, preferably 2,000 to 5,000 ppm.

In one embodiment, the sulfur-containing hydrocarbon stream is contactedwith the first adsorbent at a space velocity in the range of 50 to10,000 h⁻¹, preferably 100 to 9,000 h⁻¹, preferably 500 to 8,000 h⁻¹,preferably 800 to 7,000 h⁻¹, preferably 1,000 to 6,000 h⁻¹, preferably1,200 to 5,000 h⁻¹, preferably 1,500 to 4,000 h⁻¹, preferably 2,000 to3,000 h⁻¹. The term “space velocity” as used herein refers to a ratio ofthe volumetric flow rate of the influent of a reactor (i.e. thesulfur-containing hydrocarbon stream) to a volume of the reactor (i.e.the first vessel). Space velocity indicates how many reactor volumes ofa feed can be treated per unit time. For example, a reactor with a spacevelocity of 5 h⁻¹ is capable of processing a feed with a volume that isequivalent to five times the reactor volume in each hour.

In one embodiment, a concentration of sulfur compounds in the partiallydesulfurized hydrocarbon stream 138 s is 10% to 90%, preferably 15% to80%, preferably 20% to 70%, preferably 25% to 60%, preferably 30% to55%, preferably 35% to 50%, relative to the concentration of the sulfurcompounds in the sulfur-containing hydrocarbon stream. For example, inone embodiment, a concentration of sulfur compounds in thesulfur-containing hydrocarbon stream is in the range of 10 to 1000 ppm,preferably 50 to 800 ppm, preferably 100 to 700 ppm, preferably 150 to600 ppm, preferably 200 to 500 ppm, wherein a concentration of sulfurcompounds in the partially desulfurized hydrocarbon stream is in therange of 2 to 200 ppm, preferably 10 to 160 ppm, preferably 20 to 140ppm, preferably 30 to 120 ppm, preferably 40 to 100 ppm. Preferably, aconcentration of the combustible compounds in the partially desulfurizedhydrocarbon stream is substantially the same as the concentration of thecombustible compounds in the sulfur-containing hydrocarbon stream. Sincesulfur compounds present in the partially desulfurized hydrocarbonstream are further removed via another adsorptive desulfurizationprocess and not a hydro-desulfurization reaction, the partiallydesulfurized hydrocarbon stream preferably does not contain hydrogen, orin some embodiments, a concentration of hydrogen in the partiallydesulfurized hydrocarbon stream is no more than 2.0 vol %, preferably nomore than 1.5 vol %, preferably no more than 1.0 vol %, preferably nomore than 0.5 vol %, relative to the total volume of the partiallydesulfurized hydrocarbon stream.

Preferably, a temperature and a pressure of the partially desulfurizedhydrocarbon stream is substantially the same as that of thesulfur-containing hydrocarbon stream. For example, in some embodiments,the temperature of the partially desulfurized hydrocarbon stream is inthe range of 15 to 35° C., preferably 20 to 30° C., preferably about 25°C., and a pressure of the partially desulfurized hydrocarbon stream isin the range of 0.9 to 1.1 atm, preferably 0.95 to 1.05 atm, preferablyabout 1 atm.

The method of desulfurizing further involves delivering the partiallydesulfurized hydrocarbon stream 138 s to the second inlet 120 via theconnecting line 138 and contacting the partially desulfurizedhydrocarbon stream 138 s with the second adsorbent to form adesulfurized hydrocarbon stream 140 s.

In one embodiment, the partially desulfurized hydrocarbon stream iscontacted with the second adsorbent at a temperature of 15 to 35° C.,preferably 20 to 30° C., preferably about 25° C., and a pressure of 0.9to 1.1 atm, preferably 0.95 to 1.05 atm, preferably about 1 atm.Furthermore, the partially desulfurized hydrocarbon stream is contactedwith the second adsorbent at a space velocity in the range of 50 to10,000 h⁻¹, preferably 100 to 9,000 h⁻¹, preferably 500 to 8,000 h⁻¹,preferably 800 to 7,000 h⁻¹, preferably 1,000 to 6,000 h⁻¹, preferably1,200 to 5,000 h⁻¹, preferably 1,500 to 4,000 h⁻¹, preferably 2,000 to3,000 h⁻¹.

In one embodiment, a concentration of sulfur compounds in thedesulfurized hydrocarbon stream 140 s is 0% to 10%, preferably 0.5% to8%, preferably 0.6% to 7%, preferably 0.7% to 6%, preferably 0.8% to 5%,preferably 0.9% to 4%, preferably 1% to 3%, preferably 1.2% to 2%,relative to the concentration of the sulfur compounds in thesulfur-containing hydrocarbon stream. For example, in one embodiment, aconcentration of sulfur compounds in the sulfur-containing hydrocarbonstream is in the range of 10 to 1000 ppm, preferably 50 to 800 ppm,preferably 100 to 700 ppm, preferably 150 to 600 ppm, preferably 200 to500 ppm, wherein a concentration of sulfur compounds in the desulfurizedhydrocarbon stream is in the range of 0 to 100 ppm, preferably 0.5 to 60ppm, preferably 1 to 50 ppm, preferably 2 to 20 ppm, preferably 4 to 10ppm. Preferably, a concentration of the combustible compounds in thedesulfurized hydrocarbon stream is substantially the same as theconcentration of the combustible compounds in the sulfur-containinghydrocarbon stream. Preferably, a temperature and a pressure of thedesulfurized hydrocarbon stream is substantially the same as that of thesulfur-containing hydrocarbon stream. For example, in some embodiments,the temperature of the desulfurized hydrocarbon stream is in the rangeof to 35° C., preferably 20 to 30° C., preferably about 25° C., and apressure of the desulfurized hydrocarbon stream is in the range of 0.9to 1.1 atm, preferably 0.95 to 1.05 atm, preferably about 1 atm.

In one embodiment, a concentration of the sulfur compounds in thedesulfurized hydrocarbon stream 140 s is higher than 10 ppm, preferablyhigher than 15 ppm, preferably higher than 20 ppm, but no more than 100ppm. In view of that, the desulfurized hydrocarbon stream is deliveredto the first inlet 108 via a recycle line (not shown in figures) to becontacted with the first and the second adsorbents for a second time toreduce the concentration of the sulfur compounds of the desulfurizedhydrocarbon stream to a value less than 5 ppm, preferably less than 2ppm, preferably less than 1 ppm. Preferably, specification of therecycle line is substantially the same as specification of the feed line134 and the product line 140.

The desulfurized hydrocarbon stream 140 s may further be collected inthe product tank 128 via the product line 140. Furthermore, thedesulfurized hydrocarbon stream 140 s may be transferred to a combustionsystem or another unit in a refinery or a petrochemical plant forfurther processing.

In a preferred embodiment, the method of desulfurizing further involvesdelivering the solvent 136 s from the liquid reservoir 126 to the firstinlet 108 via the solvent line 136 and the second pump 132. Accordingly,a flow of the sulfur-containing hydrocarbon stream to the first vesselis stopped, for example, via a shut valve. Then, the solvent isdelivered to the first inlet 108, whereby the solvent 136 s is passedthrough the first adsorbent in the first vessel 104 and the secondadsorbent in the second vessel 116 to dissolve sulfur compounds that aredeposited on a surface of the first and the second adsorbents. Thecontaminated solvent, which has dissolved the sulfur compounds, may becollected via the product line 140 in a separate container (not shown).According to this embodiment, the first and the second adsorbents may beregenerated and are ready to be used in the desulfurizing process again.The term “regeneration” refers to a process whereby sulfur compoundspresent on a surface of an adsorbent are removed, and the adsorbent isprepared to be utilized in a desulfurizing process. In view of thisembodiment, the first and the second adsorbents are regenerated withinthe first and the second reactors, and therefore, the method does notinvolve replacing the adsorbents to an external adsorbent regenerationsystem to regenerate the adsorbent. The solvent is preferably passedthrough the first and the second adsorbents at a temperature in therange of 50 to 120° C., preferably 55 to 110° C., preferably 60 to 100°C., preferably 65 to 85° C., preferably about 70° C., for at least 5hours, preferably at least 10 hours, but no more than 24 hours.

In one embodiment, the method further involves delivering an inert gasto the first inlet, after delivering the solvent. The inert gas isdelivered to evaporate the solvent. Accordingly, the inert gas maypreferably be delivered with a temperature in the range of 150 to 350°C., preferably 180 to 300° C., preferably 200 to 280° C., preferably 220to 260° C., preferably about 250° C., and a flow rate of 0.02 to 5L/min, preferably 0.05 to 4 L/min, preferably 0.1 to 3 L/min, preferably0.2 to 2.5 L/min, preferably 0.3 to 2 L/min, preferably 0.5 to 1.5L/min, preferably 0.8 to 1 L/min. In one embodiment, the inert gas is atleast one gas selected from the group consisting of nitrogen, helium,argon, and krypton. Preferably, the inert gas is passed through thefirst and the second adsorbents with a pressure in the range of 1-10atm, preferably 1.1 to 8 atm, preferably 1.2 to 7 atm, preferably 1.3 to6 atm, preferably 1.4 to 5 atm, preferably 1.5 to 4 atm, preferably 1.6to 3 atm.

In one embodiment, a total cost of the method of desulfurizing asdescribed in the second aspect of this disclosure, is at least 20%,preferably at least 30%, preferably at least 40%, preferably at least50% lower than other existing desulfurization processes, mainly becauseregenerating the adsorbents, as described, is at least 20%, preferablyat least 30%, preferably at least 40%, preferably at least 50% lower incost than other existing methods such as thermal regeneration methods(that generally require withdrawal of the adsorbents) andultra-sonicating regeneration.

According to a third aspect, the present disclosure relates to a methodof making an adsorbent, which comprises cobalt and copper on anactivated carbon support.

The method involves mixing activated carbon particles with an aqueoussolution that includes at least one of ethanol, diethylene glycol, andsodium diacetate to form a first suspension.

The method of making the adsorbent further involves mixing and refluxinga cobalt-containing solution with the first suspension to formcobalt-containing activated carbon particles. Preferably, a weight ratioof the cobalt-containing solution to that of the activated carbonparticles is in the range of 0.5:10 to 3:10, preferably 0.75:10 to2.5:10, preferably 1.5:10 to 2:10, more preferably about 1.5:7.

In one embodiment, the cobalt-containing solution is cobalt acetate(e.g., cobalt acetate tetrahydrate) dissolved in deionized water. Inanother embodiment, the cobalt-containing solution is a nitrate orphosphate of cobalt, e.g. cobalt nitrate. Alternatively, thecobalt-containing solution may be a cobalt halide solution, with halidebeing fluoride, chloride, bromide, or iodide. Preferably, thecobalt-containing solution is first dissolved in deionized water, andthe resulting solution is then added to the first suspension, andrefluxed at a temperature in the range of 70 to 120° C., preferably 75to 110° C., preferably 80 to 100° C., for at least 6 hours, preferablyat least 8 hours, but no more than 12 hours. A pH of the resultingsolution may be adjusted to be within the range of 8 to 10, preferably8.5 to 9.5, preferably about 9. During this time, cobalt particles mayprecipitate on the activated carbon particles, and thus forming thecobalt-containing activated carbon particles.

The method of making the adsorbent further involves filtering and dryingthe cobalt-containing activated carbon particles and mixing the samewith the aqueous solution to form a second suspension. After filteringthe cobalt-containing activated carbon particles, they may be washeduntil a pH of the cobalt-containing activated carbon particles reducesto a value in the range of 5 to 7, preferably 5.5 to 6.5, preferablyabout 6. The cobalt-containing activated carbon particles may be driedat a temperature in the range of 120 to 180° C., preferably 130 to 170°C., preferably 140 to 160° C.

The method of making the adsorbent further involves mixing and refluxinga copper-containing solution with the second suspension to form theadsorbent. Preferably, a weight ratio of the copper-containing solutionto that of the activated carbon particles is in the range of 0.1:10 to3:10, preferably 0.2:10 to 2:10, preferably 0.3:10 to 1.75:10, morepreferably about 0.5:10.

In one embodiment, the copper-containing solution is copper nitratedissolved in deionized water. In another embodiment, thecopper-containing solution is an acetate or phosphate of copper, e.g.copper acetate. Alternatively, the copper-containing solution may be acopper halide solution, with halide being fluoride, chloride, bromide,or iodide. Preferably, the copper-containing solution is first dissolvedin deionized water, and the resulting solution is then added to thesecond suspension, and refluxed at a temperature in the range of 70 to120° C., preferably 75 to 110° C., preferably 80 to 100° C., for atleast 6 hours, preferably at least 8 hours, but no more than 12 hours. ApH of the resulting solution may be adjusted to be within the range of 8to 10, preferably 8.5 to 9.5, preferably about 9. During this time,copper particles may precipitate on the cobalt-containing activatedcarbon particles, and thus forming the adsorbent that includes cobaltand copper on an activated carbon support.

In one embodiment, the method of making the adsorbent further involvespreparing activated carbon particles and mixing the activated carbonparticles with an aqueous solution. Accordingly, pieces of rubberisothermally heated at a temperature of 250 to 550° C., preferably 300to 500° C., for at least 3 hours, preferably at least 4 hours,preferably at least 5 hours, but no more than 12 hours, to form a char.The char is further treated with an oxidizing agent to remove organicimpurities. The oxidizing agent is preferably hydrogen peroxide,although other oxidizing agents such as a halogen solution, potassiumnitrate, and/or nitric acid may also be used. The treated char isfurther heated isothermally at a temperature of 400 to 900° C.,preferably 600 to 900° C., preferably 800 to 900° C., for at least 3hours, preferably at least 4 hours, preferably at least 5 hours, but nomore than 12 hours, to form porous carbon particles. The porous carbonparticles may further be washed with deionized water and dried at atemperature in the range of 120 to 180° C., preferably 130 to 170° C.,preferably 140 to 160° C. Preferably, the porous carbon particles arefurther treated with an acid solution to form the activated carbonparticles. Accordingly, a weight of the porous carbon particles to avolume of the acid solution is in the range of 5 g: 100 ml to 15 g: 100ml, preferably 7 g: 100 ml to 13 g: 100 ml, preferably 9 g: 100 ml to 11g: 100 ml, preferably about 10 g: 100 ml. According to this embodiment,the porous carbon particles is refluxed in the acid solution at atemperature in the range of 80 to 110° C., preferably 85 to 105° C.,preferably about 90° C., for at least 3 hours, preferably at least 4hours, preferably at least 5 hours, but no more than 12 hours. The acidsolution is preferably an aqueous solution of nitric acid with aconcentration of 3 to 5 M, preferably 3.5 to 4.5 M, preferably about 4M.

The examples below are intended to further illustrate protocols for thesulfur removal system, the method of desulfurizing a sulfur-containingstream, and the method of making the adsorbent, and are not intended tolimit the scope of the claims.

Example 1—Adsorbent Preparation

In order to prepare the adsorbent, activated carbon (AC) particles wereformed. Accordingly, waste rubber tires were cut into small pieces, andiron wires removed from the rubber pieces. The pieces were cleaned,rinsed with distilled water, and dried at 110° C. for two hours. Thegranules were then heated to 300° C. to remove all the liquidconstituents from the char. Carbonization was performed at around 500°C. in a muffle furnace for five hours, and all adhering organicimpurities were oxidized by treating the char with hydrogen peroxide.The char was rinsed thoroughly with distilled water and dried. Thecarbon black was activated at 900° C. for 5 h, and the resultingactivated carbon was rinsed with distilled water and dried. Chemicalactivation was conducted on the prepared material using 4 M HNO₃ (7 gAC/70 ml) at 90° C. for 3 h in a reflux condenser. Finally, the AC waswashed thoroughly with distilled water and dried at 110° C. A detailedprotocol for converting waste rubber tires (WRTs) to porous carbon isoverviewed in the work of Danmaliki et al. and Salah et al. [G. I.Danmaliki, T. A. Saleh, Influence of conversion parameters of wastetires to activated carbon on adsorption of dibenzothiophene from modelfuels, Journal of Cleaner Production, 117 (2016) 50-55; T. A. Saleh, G.I. Danmaliki, Influence of acidic and basic treatments of activatedcarbon derived from waste rubber tires on adsorptive desulfurization ofthiophenes, Journal of the Taiwan Institute of Chemical Engineers, 60(2016) 460-468].

After preparation of activated carbon particles, metals wereincorporated as follows. 7 g of the prepared activated carbon wasdispersed in a mixture of ethanol and water. Then, 1.5 g of cobalt(II)acetate tetrahydrate, (CH₃COO)₂Co.4H₂O was dissolved in deionized water,and the solution of cobalt(H) acetate tetrahydrate was added dropwise tothe activated carbon mixture and stirred. The mixture was refluxed at atemperature in the range of 80 to 100° C. overnight, and the product wasfurther filtered and dried in an oven. The product includes cobalt onactivated carbon particles (i.e. Co/AC).

A similar procedure was conducted to with copper nitrate Cu(NO₃)₂.Accordingly, 7 g of the prepared activated carbon that also includescobalt (i.e. Co/AC) was dispersed in a mixture of ethanol and water.Then, 1.03 g of copper nitrate Cu(NO₃)₂ was dissolved in deionizedwater, and the solution of copper nitrate Cu(NO₃)₂ was added dropwise tothe Co/AC mixture and stirred. The mixture was refluxed at a temperaturein the range of 80 to 100° C. overnight, and the product was furtherfiltered and dried in an oven. The product includes cobalt and copper onactivated carbon particles.

Example 2—Preparation of Standard Solutions

Six separate standard solutions were prepared by dissolving six sulfuriccompounds, including thiophene (T), benzothiophene (BT),dibenzo[b,d]thiophene (DBT), 5-methyl-1-benzothiophene (MBT),4-methyldibenzo[b,d]thiophene (MDBT) and4,6-dimethyldibenzo[b,d]thiophene (DMDBT) into a liquid hydrocarbon toform fuel solutions. A a concentration of the sulfur compounds in theresulting fuel solutions were 50 ppm, 25 ppm, 5 ppm, 1 ppm, and 0.5 ppm.

Example 3—Batch Mode Desulfurization

A batch mode adsorption was conducted. Accordingly, various amounts, inthe range between 0.01 to 0.5 g of adsorbents were introduced into 15 mlof the fuel solution. The T, BT, DBT, MBT, MDBT and DMDBT initialconcentrations were 50 ppm. The refractory sulfur compounds solutionscontaining the adsorbents were mixed well under stirring at roomtemperature until equilibrium. After adsorption period, samples werecollected using a syringe filter (hydrophobic polytetrafluoroethylene)and the concentrations of the sulfur compounds were measured by gaschromatography coupled with sulfur chemiluminescence detector (GC-SCD).

Example 4—Continuous Mode Desulfurization

Fixed bed flowing system was used to test the performance of theprepared AC samples. The adsorbent was packed inside the column; modelfuel sample was then passed through the column by a peristaltic pumpwith a controlled flow rate (50 rpm) at a temperature of 25° C., asshown in FIG. 1D. Once the adsorption process was started, treated fuelswere sampled at different time intervals and injected to the GC-SCD foranalysis. The process was halted after breakthrough was reached.

The system was modified as shown in FIG. 1E for the regeneration of theabsorbent materials in fixed bed reactor using solvents. After theadsorption process was completed valves (131) and (137) were closedwhile valves (135) and (139) were opened. Then, a binary mixture oforganic solvents (50/50 vol % methanol/toluene) was injected into thepacked column to regenerate the used absorbent material and prepare itfor another adsorption process.

Fluidized bed reactor system was used to increase the liquid-solidcontact area and to enhance the absorbent performance, as shown in FIG.1C. The model fuel was pumped to the system at a different flow rate.Then, the flow rate was fixed once the absorbent particles weresuspended in the injected fluid and the desired bed expansion wasobtained. Finally, the reactor output was sampled and analyzed.

As shown in FIG. 1F, the experimental setup consists oflaboratory-scaled fluidized and fixed bed reactor in series, flow meter,two hold-up tanks, valves, peristaltic pump, and GC-SCD analyzer. Thefluidized bed column is a two-phase reactor and it is made from quartztube with (20-30 cm) in length and (1-1.5 cm) inside diameter. Toprevent loss of the used material from the lower and upper part of thecolumn, two pieces of standard screen mesh were installed and fixed.While the fixed bed reactor has a length (20-30 cm) and a diameter(1-1.5 cm), the absorbent material was packed in the column, as shown inFIG. 1F.

Example 5—Adsorbent Regeneration

Referring now to FIG. 1G. Initially, valves (131) and (151) were openedand the model fuel was injected into the fluidized bed reactor at acertain volumetric flow using a peristaltic pump. Then, the volumetricflow of the model fuel was increased gradually until the absorbentparticles were suspended in the fluid and a required bed expansion wasobtained. The output of the fluidized bed reactor was transported intothe fixed bed reactor for further adsorption. Finally, the treated fuel,which is the output of the fixed bed reactor, were sampled and injectedto a gas chromatography (GC) with a sulfur chemiluminescence detector(SCD) at different time periods. The adsorption process was stopped oncethe breakthrough was achieved and then the valves (131) and (151) wereclosed. Then, valves (135), (155), and (157) were opened and a binarymixture of organic solvents (50/50 vol % methanol/toluene) were injectedsimultaneously to both columns, and a desorption occurred in order toregenerate the particle absorbents for another adsorption process.

Performance of an effective regeneration process for the used absorbentmaterials in the desulfurization process is very important in economicpoint. Different techniques have been suggested for the regenerationprocess including, solvent regeneration, thermal regeneration andultra-sonication regeneration [Han, Xue, Erin Wishart, and Ying Zheng. Acomparison of three methods to regenerate activated carbon saturated bydiesel fuels., The Canadian Journal of Chemical Engineering 92, no. 5(2014), 884-891]. The used absorbent materials in all the differentsystem designs were regenerated subsequently. The used regenerationmethod was the solvent washing using a binary mixture of organicsolvents (50/50 vol % methanol/toluene). This solvent was induced to thesystem columns at 70 C until there is no sulfur detected by GC-SCD inthe used solvent. To guarantee that there are no absorbed solventmolecules in the regenerated absorbent, it has been heated up to 300 Cfor 1 h and flushed with inert gas N₂ simultaneously with a flow rate 40ml/min [Velu, S., Shingo Watanabe, Xiaoliang Ma, and Chunshan Song,“Regenerable adsorbents for the adsorptive desulfurization oftransportation fuels for fuel cell applications.”, Chem. Soc., FuelChem. Div. Prepr 48 (2003), 526-528]. The solvent washing method hasseveral advantages over other regeneration methods. For example, it isenvironmentally friendly technique since it does not produce harmfulgasses which are the case in the oxidative and reductive regenerationtechniques [C. Song, Fuel processing for low-temperature andhigh-temperature fuel cells: challenges, and opportunities forsustainable development in the 21st century, Catal. Today 77 (2002),17-49].

Example 6

In order to study the effect of the contact time on the adsorptionprocess using AC/CoCu nanoparticles, the removal rate of the sulfurq_(t) (mmol/g) were plotted against the contact time for the testedsulfur compounds, as shown in FIG. 2. It can be observed that theinitial sulfur removal increased rapidly at the first 20 minutes of thebatch adsorption process for all the sulfuric compounds. Then, theadsorption rate increased gradually until the equilibrium state wasestablished. A large number of the available active sites can explainthe high sulfur removal rate at the initial stage of the adsorptionprocess, which enables the adsorbent to adsorb a large number of thesulfur molecules. The number of the available active sites decreaseswith time, which leads to reducing the sulfur removal rate. Furthermore,the molecules are adsorbed into the macropores and mesopores at thebeginning of the adsorption process, while they have to penetrate deepertoward micro-pores in the next stages of the adsorption process. As aresult, the sulfur removal rate was reduced due to the increasing in theresistance to the molecule diffusion.

Example 7

The adsorptive desulfurization is reiterated to evaluate the adsorptionperformance of the AC/CoCu adsorbents. As depicted in FIG. 3, thefixed-bed, laboratory-scale reactor comprised a low-flow liquid rotarypiston pump, a feed tank, a valve, a custom-made column backed with thematerial, and a collecting tank. During continuous liquiddesulfurization, the fuel containing the six sulfur compounds wasallowed to pass through the fixed bed in an up-flow direction. Theeffluent was sampled periodically, and the evolution of sulfurconcentrations was measured by GC-SCD.

The plots of the total thiophene concentrations (C/C_(o)) againstcumulative time provided breakthrough curves for each of the adsorbedrefractory sulfur compounds in FIG. 3. At the early period of theadsorption, both T and BT were above 0 ppm while others were almost 0ppm up to about 100 min of adsorption. None of the studied refractorysulfur compounds reached its initial concentration until 540 min. TheAC/CoCu worked efficiently for simultaneous adsorptive desulfurizationin the order as DBT>MDBT>DMDBT>MBT>BT>Thiophene.

After desulfurization, the saturated adsorbent was subjected to aregeneration treatment by washing with a binary mixture of organicsolvents (50/50 vol % methanol/toluene). The evolution of sulfurconcentrations in the regeneration effluent was measured by GC-SCD. Thewashing step was followed by bed heating up to 180° C. under acontinuous inert flow of around 1 L-min⁻¹ N₂ in order to remove theremaining solvent. With this strategy of regeneration, after five cyclesperformed in total, the efficiency of the regenerated AC/CoCu adsorbentremained relatively stable. The combination of the fluidized system withthe fixed system provided almost twice enhancement in the breakthroughcomparing with the single fixed bed system.

1: A sulfur removal system, comprising: a first reactor comprising afirst vessel having a first internal cavity with a first adsorbent bedthat contains a first adsorbent, a first inlet located proximal to abottom of the first vessel, and a first outlet located proximal to a topof the first vessel; and a second reactor comprising a second vesselhaving a second inlet, a second outlet, and a second internal cavitywith a second adsorbent bed that contains a second adsorbent, whereinthe first and the second adsorbents comprise cobalt and copper on anactivated carbon support, wherein the first adsorbent bed has across-sectional area that is substantially the same as a cross-sectionalarea of the first vessel, and wherein the second inlet is fluidlyconnected to the first outlet via a connecting line. 2: The system ofclaim 1, wherein the first and the second adsorbents are substantiallythe same. 3: The system of claim 1, further comprising a lower meshstructure located in the first internal cavity and proximal to thebottom of the first vessel and an upper mesh structure located in thefirst internal cavity and proximal to the top of the first vessel,defining the first adsorbent bed. 4: The system of claim 3, wherein thefirst adsorbent has a particle size in the range of 0.5 to 10 mm, andwherein the lower and the upper mesh structures have a mesh size of lessthan 0.5 mm. 5: The system of claim 1, wherein the first reactor is afluidized-bed reactor. 6: The system of claim 5, wherein the secondreactor is a fixed-bed reactor. 7: The system of claim 6, wherein thesecond inlet is located proximal to a top of the second vessel and thesecond outlet is located proximal to a bottom of the second vessel. 8:The system of claim 6, wherein the second inlet is located proximal to abottom of the second vessel and the second outlet is located proximal toa top of the second vessel. 9: The system of claim 1, furthercomprising: a liquid reservoir located upstream of and fluidly connectedto the first inlet via a solvent line, wherein the liquid reservoir isconfigured to deliver a solvent to the first and the second internalcavities to regenerate the first and the second adsorbents. 10: A methodof desulfurizing a sulfur-containing hydrocarbon stream with the sulfurremoval system of claim 1, comprising: delivering the sulfur-containinghydrocarbon stream to the first inlet and contacting thesulfur-containing hydrocarbon stream with the first adsorbent to form apartially desulfurized hydrocarbon stream; and delivering the partiallydesulfurized hydrocarbon stream to the second inlet and contacting thepartially desulfurized hydrocarbon stream with the second adsorbent toform a desulfurized hydrocarbon stream. 11: The method of claim 10,wherein the sulfur-containing hydrocarbon stream is contacted with thefirst adsorbent at a temperature of 15 to 35° C. and a pressure of 0.9to 1.1 atm, and wherein the partially desulfurized hydrocarbon stream iscontacted with the second adsorbent at a temperature of 15 to 35° C. anda pressure of 0.9 to 1.1 atm. 12: The method of claim 10, wherein thesulfur-containing hydrocarbon stream comprises at least one sulfurcompound selected from the group consisting of a thiophene, abenzothiophene, a dibenzothiophene, a methyl benzothiophene, a methyldibenzothiophene, and a dimethyl dibenzothiophene. 13: The method ofclaim 10, wherein a concentration of sulfur compounds in thesulfur-containing hydrocarbon stream is at least 50 ppm, and wherein aconcentration of sulfur compounds in the desulfurized hydrocarbon streamis no more than 5 ppm. 14: The method of claim 10, wherein the sulfurremoval system further comprises a liquid reservoir located upstream ofand fluidly connected to the first inlet via a solvent line, the methodfurther comprising: delivering a solvent to the first inlet toregenerate the first adsorbent and the second inlet to regenerate thesecond adsorbent. 15: The method of claim 14, wherein the firstadsorbent is regenerated within the first reactor and the secondadsorbent is regenerated within the second reactor. 16: The method ofclaim 14, further comprising: delivering an inert gas to the first inletto evaporate the solvent, after delivering the solvent. 17: The methodof claim 16, wherein the inert gas is nitrogen gas with a temperature inthe range of 150 to 350° C., which is delivered with a flow rate of 0.02to 5 L/min. 18: A method of making an adsorbent, which comprises cobaltand copper on an activated carbon support, the method comprising: mixingactivated carbon particles with an aqueous solution comprising at leastone of ethanol, diethylene glycol, and sodium diacetate to form a firstsuspension; mixing a cobalt-containing solution with the firstsuspension and refluxing to form cobalt-containing activated carbonparticles; filtering and drying the cobalt-containing activated carbonparticles and mixing the same with the aqueous solution to form a secondsuspension; and mixing and refluxing a copper-containing solution withthe second suspension to form the adsorbent. 19: The method of claim 18,further comprising: isothermally heating a rubber at a temperature of250 to 550° C. to form a char; treating the char with an oxidizing agentto remove organic impurities; isothermally heating the char at atemperature of 400 to 900° C.; and treating the char with an acidsolution to form the activated carbon particles, prior to mixing theactivated carbon particles with the aqueous solution. 20: The method ofclaim 18, wherein the cobalt-containing solution is cobalt acetatedissolved in deionized water, and wherein the copper-containing solutionis copper nitrate dissolved in deionized water.